The present invention relates in general to ophthalmic implants, and in particular to a new and useful transcleral apparatus for the draining of aqueous humor from the anterior chamber of the eye.
In the past when surgical treatment for glaucoma has been attempted, it has been directed toward creating one or more outflow tracts for the aqueous humor, the liquid which fills the anterior part of the eye. In so doing, intraocular pressure has been reduced and the continued damage to the optic nerve by elevated pressures, has been slowed or halted.
A problem frequently encountered with the creation of an outflow tract is the closing-off or "fibrosis" of the aqueous channel causing a return to the high pressure state in the eye. In an effort to thwart such closing of the drainage tracts, numerous synthetic conduits have been designed and implanted. Without exception these devices are implanted using a conventional surgical approach by creating a flap in the external surface of the eye, allowing access to the intraocular environment "from the outside in". No one device has met with overwhelming success, however. The most frequently encountered problems are:
1. Closing-off of the implanted drain by fibrosis and, thus, a return to a poor outflow state.
2. Excessive outflow leading to a soft, poorly formed eye.
3. Infection which is secondary to the surgical disruption of the eye's anatomic barriers.
A recent advance in this field has been the use of laser technology to create a fistula from within the anterior chamber of the eye. This fistula extends only to the subconjunctival space, leaving the eye's natural barrier--the conjunctiva--entirely intact. This fistulous tract is created using a laser light source delivered at point blank range focussed by a thin fiberoptic tip that is introduced through a small (1/2 mm.) incision in the peripheral cornea. This procedure is routine and relatively well-tolerated. This technique has come to be known as a "laser sclerotomy ab interno".
Like the older, manually-created filtering procedures, the laser tracts have closed-off with time. It is specifically for maintaining the patency of these filtration sclerotomies, including but not limited to those created by laser, that the apparatus of the present invention has been conceived.
U.S. Pat. No. 3,159,161 to Ness discloses a transcleral implant extending through the trabecular meshwork for controlling glaucoma. The implant has a tubular projection which extends into a surgically drilled hole in the trabecular meshwork and into the anterior chamber of the eye. A curved channel which follows the curvature of the eyeball extends from the projection for draining fluid from the anterior chamber. The implant does not have a conical flange nor an interior valve nor does it have an outlet end with a cage as in the present invention.
The use of a valve for venting fluid from the interior of an eyeball is known per se from U.S. Pat. No. 4,402,681 to Haas et al. The valve structure is installed at a location remote from the anterior chamber, however.
Another approach in treating glaucoma using an implant is disclosed by U.S. Pat. No. 4,428,746 to Mendez. The implant is in the form of a bent synthetic cylindrical member which is surgically positioned under a scleral flap near the trabecular meshwork.
U.S. Pat. No. 4,457,757 to Molteno discloses a tubular implant for draining aqueous humor from the eye to relieve glaucoma. One end of the tube is fitted with a flange for insuring a firm attachment to the eye.
A far more complex implant for relieving glaucoma is disclosed by U.S. Pat. No. 4,521,210 to Wong. The implant lies between the sclera and the choroid or ciliary body of the eye and does not extend through the sclera.
The use of a transcleral tube near the trabecular meshwork of the eye is disclosed by U.S. Pat. No. 4,604,087 to Joseph. The tube is secured by a large band which extends around a major diameter of the eyeball.
A surgically implanted member is taught by U.S. Pat. No. 4,634,418 to Binder, for communicating with the anterior chamber of the eye to drain fluid therefrom by a wicking action.
A method of installation for an intraocular lens using a laser is taught by U.S. Pat. No. 4,738,680 to Herman.
A need remains for an ophthalmic implant which is securely held in the eye in a manner which avoids infection and which avoids the closing-off of the outflow of a aqueous humor, while at the same time avoiding excessive outflow of fluid from the eye.